Modified Project Summary/Abstract Section Yogic breathwork is a low-risk low-cost mind-body therapy that can be easily learned and performed without any additional equipment. The practices of yogic breathwork have been demonstrated to be effective for a wide range of health conditions including sleep and neurological conditions. While underlying mechanisms are still not fully known, one previously studied mechanism for the health benefits of yogic breathwork is through parasympathetic activation as evidenced by decreased respiration rate, heart rate and blood pressure, and increased heart rate variability. Another mechanism for explaining the health benefits of yogic breathwork can be its direct influence on cerebrospinal fluid (CSF) circulation, which to date has not been investigated due to lack of non-invasive methodology. CSF circulates by bulk flow (macrocirculation) around the central nervous system (CNS) while ensuring the health of the CNS. CSF undergoes periodic pulsations due to arterial pulsation and respiration. While cardiac-driven CSF has been studied extensively, respiratory-driven CSF is not very well-understood due to lack of real-time non-invasive approaches. To address this gap, we have recently developed a real-time phase-contrast magnetic resonance imaging (RT-PCMRI) technique, and demonstrated that deep slow abdominal breathing - compared to natural breathing - increases the amplitude of the CSF flow velocities while lowering the frequency of respiratory-driven CSF flow, suggesting that breathing patterns have quasi-immediate influence on the modulation of CSF circulation. Additionally, CSF circulation plays a central role in maintaining glymphatic function (microcirculation), which is a recently identified brain-wide cleaning mechanism that supports the rapid interchange of CSF and interstitial fluid (ISF), and facilitates the clearance of solutes and metabolic wastes from the brain interstitium, preferentially during sleep compared to wakefulness. In order to evaluate glymphatic function in human brain, we have recently developed a novel non-invasive imaging approach incorporating simultaneous polysomnography and magnetic resonance spectroscopy measurements across sleep-wakes cycles, which indicated enhanced glymphatic activity during sleep, particularly in slow wave sleep. Because we know that the entry of CSF along perivascular channels facilitates glymphatic function in rodents, we hypothesize that the influence of yogic breathwork on CSF flow dynamics will also facilitate the glymphatic activity. Because we know yoga improves sleep, and glymphatic function is mainly active during sleep compared to the wakefulness, we expect that a regular practice of yogic breathwork will improve sleep quality, and will benefit the glymphatic activity. Thus, we propose to: (1) determine the influence of an 8-week yogic breathwork intervention on CSF flow dynamics; (2) determine the influence of an 8-week yogic breathwork intervention on CSF circulation (flow dynamics and glymphatic function), and; (3) measure the effects of the breathwork intervention on participants? long-term sleep patterns, and correlate the degree of sleep improvement with the changes in CSF circulation measured in Aim 2.